The running quality of the air solves the problem of system pressure drop and the energy saving effect is remarkable.

0刖Laigang cold rolling production line mainly includes a push-pull pickling unit, a single-stand reversing mill, a rewinding unit and supporting air compressor stations, acid regeneration and wastewater treatment stations.

1 Process flow and user usage The compressed air of the production line is provided by the plant air compressor station. There are 3 air compressors in the station. Each volume flow rate is 81m/min. It is dual-use and one-time during normal production. The process flow is shown in the production line. The average gas consumption is 3900m/h and the maximum gas consumption is 4500m/h. The main users and dosages are shown in Table 1.

Table 1 Production line compressed air main users and dosage user pressure average dosage) user pressure average dosage pickling unit oil and gas lubrication station acid regenerative rolling mill purging rewinding unit rolling mill thickness gauge emulsion station laser speedometer strip transmission equipment brake wastewater Handle the station to run the work.

2 System problems 2.1 System instantaneous pressure fluctuations The compressed air system of the production line adopts straight pipe type piping. Due to the imbalance of gas consumption of each gas point, the instantaneous flow rate of the mill purge emulsion can be as high as 70m/min. 0.3 ~ 0.68MPa lost to about 0. MPa, which is relatively stable for the gas source, the instantaneous impact of the meter gas is too large, and the brake gas and the acid regeneration gas are caused by the high pressure of the rolling mill. The serious threat has become a major bottleneck restricting the safe and efficient production of the production line.

2.2 Air compressor loading and unloading Frequent air compressor outlets are equipped with degreasers, dryers and filters.

As the time of use increases, the pressure drop of the filter increases and the resistance of the compressed air to the gas storage tank increases. When the air compressor is loaded, the flow rate passed cannot reach the gas flow generated by the air compressor, the pressure rapidly rises to the unloading pressure, and the air compressor is quickly unloaded. When the pressure remaining in the pipeline is quickly reduced to the loading pressure, the air compressor is immediately loaded and operated, and the number of switching per minute is as high as 3 to 5 times, which seriously affects the use of the intake valve and the bearing and the motor on the air compressor body. life. At the same time, the internal pressure is high and the current is large (average 30A), which increases the running cost.

2.3 System efficiency is low The dryer in the system uses a heat-free regenerative adsorption dryer. The regenerative gas consumption is up to 12m/min. The actual air output of the air compressor is only 61m/min after passing through three filtering devices. The average gas consumption of the production line is 65m/min. In order to ensure the normal operation of the production, only two air compressors can be operated, resulting in a low operating load rate of the air compressor, with an average of only 53%, and the system is in an inefficient operation state. Moreover, the waste gas treatment station and the acid regeneration gas are not synchronized with the production line. When the production line is overhauled, an air compressor is still needed to meet the gas demand of the equipment, resulting in great waste of energy.

4 Mill purge air consumption excessive mill pressure sweep system is used to clean the emulsion on the surface of the steel strip. It has high requirements on the cleanliness of the gas source and the stability of the gas supply pressure. The gas supply characteristics are continuous with the rolling rhythm. Gas supply, no gas supply at the moment of replacement. The system consumes a large amount of gas and has high operating cost. The gas supply network of the gas supply pipe network and the rolling steel belt transmission equipment is supplied to the same pipe, which indirectly causes instability of the gas pressure of the brake gas system of the rolling mill steel belt transmission equipment. .

3 Reconstruction plan 1 Optimize the process route of the air compressor station. After the air outlet of the air compressor is directly connected to the gas storage tank, the gas storage tank is connected to the degreaser, the dryer and the filter in turn, as shown in the figure. The gas tank can realize the buffering effect and reduce the resistance of the system, thereby extending the residence time of the unloading and unloading, and reducing the current during unloading.

Process of compressed air system after reformation 3.2 Adopting gas storage tank and check valve partial pressure air supply mode Rolling mill belt conveyor equipment brake gas is characterized by small gas consumption, only om / h but high gas pressure requirements, must be greater than 0.5MPa In order to avoid the excessive pressure of the mill to purge the emulsion, the system pressure is too low, resulting in the transmission brake device not working. The gas cylinder and the check valve are combined to supply the brakes. The process brakes processQPtimztionandEnerg3-saving The gas pressure is as shown.

According to the working system of the rolling mill, a gas storage tank with an volume of im is added. When the system pressure is increased during the intermittent change of the strip (average of about 3 minutes), the system inflates the coiler to the coiler until the supervisor The pressure is consistent; during the rolling process, when the system pressure is reduced, the compressed air in the coiler's gas storage tank will not flow to the main line through the check valve, which is specially used for the coiler's brake gas to meet the brake gas. demand.

3.3 Adopting a combined gas supply method to add a small air compressor of 11m/mn and a gas storage tank of 6m in the acid regeneration area, together with the original gas storage tank, to supply acid regeneration gas during maintenance, without running large air pressure Machine as shown. During the non-overhaul period, the check valve is adopted to fill the tank with the pressure in the gap of the rolling mill to increase the pressure reserve at the peak gas point. During the normal rolling process of the rolling mill, the pressure of the system is not maintained. The main line leaks to ensure proper operation of acid regeneration.

3.4 Stabilizing the system pressure to rebuild the gas supply pipe network, separate the purge gas pipe network from the brake gas pipe network of the rolling mill steel strip transmission equipment, change the structure of the purge pipe, change the nozzle form and the purge height and angle to improve the purge The effect is to reduce the amount of gas used and stabilize the pressure of the system.

4 transformation effect through transformation, the average gas consumption of the production line is reduced to 3100m / h air compressor operation from the original two continuous gas supply, changed to only one, the air compressor is also reduced to an average of every 2 hours 1 time, the unloading current is reduced from the original average of 33. 5A to 30.8A, which prolongs the service life of the intake valve, bearing and motor, improves the running quality of the compressed air, and completely solves the problem of system pressure drop. While saving energy and stabilizing the operation of the system, it meets the gas demand of all users of the production line, and the net benefit per year is 450kW and the net benefit is 1.8 million yuan.

Guest Editor: Yao Youling

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